This application is based upon and claims the benefit of Japanese Patent Applications No. 11-145323 filed on May 25, 1999, the contents of which are incorporated herein by reference.
1. Field of the Invention
This invention relates to heat exchangers suitable for a radiator, an evaporator, or the like in a refrigerating cycle.
2. Description of the Related Art
JP-A-1-351783 proposes a heat exchanger in which, as shown in FIG. 15A, notch portions 211a indicated with slant lines are provided at both long-side end portions of a tube 211 to reduce a size of the heat exchanger in a direction parallel to an air flow direction.
On the other hand, as shown in FIG. 15B, a tube 211, which is generally used at a high internal pressure state for a heat exchanger such as a condensers a radiator, or a heat exchanger of a super critical refrigerating cycle, adopts a multi-hole structure having several passage holes 211b arranged in the cross-sectional long-side direction thereof, thereby improving a withstand pressure of the tube 211. The super critical refrigerating cycle uses refrigerant such as carbon dioxide, ethylene, ethane, or nitrogen oxide, a pressure of which exceeds a super critical pressure.
However, it has been revealed by the inventors that the following problems were liable to occur when the structure proposed in JP-A-11-351783 was applied to the tube 211 having the multi-hole structure. Specifically, the passage holes 211b are formed at the same time when the tube 211 is formed by extrusion molding or the like. If the notch portions 211a are formed on the tube 211 by cutting after the passage holes 211b are formed, as shown in FIG. 16A, the cut surface is liable to be crushed at a vicinal region of the passage holes 211b. When the cut surface is crushed to form a crushed portion 160 and the tube 211 is inserted into a header tank with the crushed portion 160, the crushed portion 160 forms a space between the tube 211 and the header tank, and the space induces joining failure (welding failure) therebetween readily. Further, if the tube 211 has manufacture variations when it is formed and it is cut, as shown in FIG. 16B, one of the passage holes 211b may be cut. The cut hole 211b forms a space (gap), which can induce the joining failure between the tube 211 and the header tank readily.
The present invention has been made in view of the above problems. An object of the present invention is to prevent joining failure between a multi-hole structured tube and a header tank in a heat exchanger.
According to the present invention, a tube for a heat exchanger has an end portion in a longitudinal direction thereof. The end portion is formed by a cut surface, which extends in the longitudinal direction of the tube and defines an end portion width, which is smaller than a tube width at a portion of the tube other than the end portion. The end portion width and the tube width are perpendicular to the longitudinal direction and parallel to a cross-sectional long side direction of the tube. The tube has a plurality of passage holes arranged in the cross-sectional long side direction within the end portion width, and a hole of the passage holes disposed most adjacently to the cut surface defines a specific distance xcex40 from the cut surface.
Accordingly, the hole and the cut surface can be prevented from being crushed when the cut surface is formed. When the end portion of the tube is inserted into a header tank, no gap is produced between the tube and the header tank, thereby preventing joining failure between the tube and the header tank.